Metabolic responses of tropical trees to ozone pollution.

Plants fumigated with 40ppbv, 80ppbv and 120ppbv concentrations of O3 exhibited significant reduction in total chlorophyll content, RuBP carboxylase activity and net photosynthesis. The reduction in total chlorophyll activity ranged from 12 to 36% in Bauhinia variegata, 11 to 35% in Ficus infectoria and 3 to 26% in Pongamia pinnata on fumigation with O3, while the RuBP carboxylase activity was reduced by 10 to 32% in Bauhinia variegata, 10 to 23% in Ficus infectoria and 9 to 15% in Pongamia pinnata. The net photosynthesis was also reduced by 6 to 26% in B. variegata, 16 to 39% in F. infectoria and 7 to 31% in P. pinnata on fumigation with 03. The relative higher sensitivity of tropical trees to O3 suggests that the ambient air quality standards in tropical tree areas need to be stringent to prevent vegetation from air pollution.

Copper effect on photosynthesis and transpiration in safflower.

The young leaves of safflower plants subjected to deficient supply of copper (0.00063 mg Cu L-1) developed visible symptoms of Cu deficiency and showed a decrease in chlorophyll concentration, Hill activity, net photosynthesis and transpiration. On giving normal supply of Cu (0.063 mg Cu L-1), these changes were partially reversed.